1. Field
The present disclosure is directed to a magenta toner for developing electrostatic latent images.
2. Description of the Related Art
Recently, a demand for high-quality printed color images has been increasing. In a typical digital color copier or printer, an original color image is divided by color via blue, green, and red filters, and a latent image corresponding to the original color image is developed by using toner of yellow, magenta, and cyan, which, respectively, are complementary colors of blue, green, and red, and black toner. Accordingly, a colorant in toner largely affects an image quality (for example, tone, transparency, and color reproduction). Among various color toners, magenta toner plays an important role in reproducing a tone of the skin. In addition, since the skin tone of a human subject is a half tone, excellent developability is desired for magenta toner. Given this need, as a conventional colorant for magenta toner, a quinacridone colorant, a thioindigo colorant, a xanthene colorant, a monoazo colorant, a perylene colorant, and a diketo-pyrrolo-pyrrole (DPP) colorant are well known.
In general, when a pigment is used as a magenta colorant, high light-fastness may be obtained. But, its tone and transparency may not be sufficient. For example, to improve these characteristics, JP 1997-255882 A discloses that a pigment may be finely-dispersed in various media. However, it is difficult to allow a pigment included in a toner prepared by the conventional toner preparation procedure to have a sufficiently fine particle diameter. Also, it is difficult to homogeneously disperse fine pigment particles in a toner.
As a method to enlarge a color gamut, for example, a full-color image forming method has been suggested. The full-color image forming method utilizes a 5 or more color toner set including orange toner or red toner, in addition to yellow toner, magenta toner, cyan toner and black toner. In the method, colors in the 360 degree range of the munsell color circle-chart are reproduced by additionally using orange toner or red toner in addition to a yellow toner, a magenta toner, and a cyan toner, thus, enlarging a color reproduction region. For example, JP 2007-304401 A discloses that an orange toner using an orange colorant, such as C. I. pigment orange 1, 11 or the like, is used to enlarge a color reproduction region from a red region to an orange region. Also, JP 2011-242431 A discloses that red toner using a red colorant, such as C. I. vat red 41 is used to enlarge a color reproduction region from a red region to an orange region. These methods, however, require a complicated developing system, and thus require a complicated control, thereby, making it difficult to ensure a high quality image to be obtained.
JP 2000-181170 A discloses a toner in which a fluorescent colorant is added to a colorant to obtain improved brightness, enlarged color reproduction region, and improved color tone. However, since a wavelength region outside a main wavelength region of an absorption spectrum has an absorption area of 98% or less, it is difficult to enlarge a color reproduction region while the color quality is maintained. Also, the high demand for high-quality images has led to the high demand for more finely divided toner particles having a smaller particle diameter. However, when known oxide inorganic fluorescent substances are more finely divided for the addition into the more finely divided toner particles, fluorescent characteristics of the inorganic fluorescent substance may deteriorate. Accordingly, improvement in color reproduction effects is insufficient.
Thus, as described above, to improve the quality of a printed color image, to obtain excellent transparency of a printed color image, or to obtain a printed color image that is closer to an original image thereof, there is an increasing need to develop magenta toner having improved tone, chroma, and electrophotographic properties.